Power converters generally have a component that transforms a voltage from a first value to a second value. Inevitably, there are constraints on just what the second value can be. These constraints define the operating range of the power converter.
One way to extend the operating range of a power converter is to reconfigure it so that it operates in a different operating mode. This can be done on-the-fly, while the power converter is actually operating. This results in a new operating range.
There is, however, a drawback to doing so.
In most physical systems, any sort of step change tends to bring with it some kind of transient response. Eventually, the transient dies down and a new steady-state prevails. However, even short transients are potentially troublesome in a power converter.